doReconnectAndCatchUp() now uses the replicaFlushedLSN returned by
the reconnect handshake as the catch-up start point, not the
shipper's stale cached value. The replica may have less durable
progress than the shipper last knew.
ReplicaReceiver initialization: flushedLSN now set from the
volume's checkpoint LSN (durable by definition), not nextLSN
(which includes unflushed entries). receivedLSN still uses
nextLSN-1 since those entries are in the WAL buffer even if
not yet synced.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds the sync_all reconnect protocol: when a degraded shipper
reconnects, it performs a handshake (ResumeShipReq/Resp) to
determine the replica's durable progress, then streams missed
WAL entries to close the gap before resuming live shipping.
New wire messages:
- MsgResumeShipReq (0x03): primary sends epoch, headLSN, retainStart
- MsgResumeShipResp (0x04): replica returns status + flushedLSN
- MsgCatchupDone (0x05): marks end of catch-up stream
Decision matrix after handshake:
- R == H: already caught up → InSync
- S <= R+1 <= H: recoverable gap → CatchingUp → stream → InSync
- R+1 < S: gap exceeds retained WAL → NeedsRebuild
- R > H: impossible progress → NeedsRebuild
WALAccess interface: narrow abstraction (RetainedRange + StreamEntries)
avoids coupling shipper to raw WAL internals.
Bootstrap vs reconnect split: fresh shippers (HasFlushedProgress=false)
use CP13-4 bootstrap path. Previously-synced shippers use handshake.
Catch-up retry budget: maxCatchupRetries=3 before NeedsRebuild.
ReplicaReceiver now initializes receivedLSN/flushedLSN from volume's
nextLSN on construction (handles receiver restart on existing volume).
TestBug2_SyncAll_SyncCache_AfterDegradedShipperRecovers flips FAIL→PASS.
All previously-passing baseline tests remain green.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Barrier response extended from 1-byte status to 9-byte payload
carrying the replica's durable WAL progress (FlushedLSN). Updated
only after successful fd.Sync(), never on receive/append/send.
Replica side: new flushedLSN field on ReplicaReceiver, advanced
only in handleBarrier after proven contiguous receipt + sync.
max() guard prevents regression.
Shipper side: new replicaFlushedLSN (authoritative) replacing
ShippedLSN (diagnostic only). Monotonic CAS update from barrier
response. hasFlushedProgress flag tracks whether replica supports
the extended protocol.
ShipperGroup: MinReplicaFlushedLSN() returns (uint64, bool) —
minimum across shippers with known progress. (0, false) for empty
groups or legacy replicas.
Backward compat: 1-byte legacy responses decoded as FlushedLSN=0.
Legacy replicas explicitly excluded from sync_all correctness.
7 new tests: roundtrip, backward compat, flush-only-after-sync,
not-on-receive, shipper update, monotonicity, group minimum.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
ReplicaReceiver.DataAddr()/CtrlAddr() now return canonical ip:port
instead of raw listener addresses that may be wildcard (:port,
0.0.0.0:port, [::]:port).
New canonicalizeListenerAddr() resolves wildcard IPs using the
provided advertised host (from VS listen address). Falls back to
outbound-IP detection when no advertised host is available.
NewReplicaReceiver accepts optional advertisedHost parameter for
multi-NIC correctness. In production, the assignment path already
provides canonical addresses; this fix ensures test patterns with
:0 bind also produce routable addresses.
7 new tests. TestBug3_ReplicaAddr_MustBeIPPort_WildcardBind flips
from FAIL to PASS.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds sync.RWMutex (ioMu) to BlockVol enforcing mutual exclusion
between normal I/O and destructive state operations.
Shared (RLock): WriteLBA, ReadLBA, Trim, SyncCache, replica
applyEntry, rebuild applyRebuildEntry — concurrent I/O safe.
Exclusive (Lock): RestoreSnapshot, ImportSnapshot, Expand,
PrepareExpand, CommitExpand, CancelExpand — drains all in-flight
I/O before modifying extent/WAL/dirtyMap.
Scope rule: RLock covers local data-structure mutation only.
Replication shipping is asynchronous and outside the lock, so
exclusive holders block only behind local I/O, not network stalls.
Lock ordering: ioMu > snapMu > assignMu > mu.
Closes the critical ER item: restore/import vs concurrent WriteLBA
silent data corruption gap.
3 new tests: concurrent writes allowed, real restore-vs-write
contention with data integrity check, close coordination.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add SimulatedMaster test helper + 20 assignment sequence tests (8 sequence,
5 failover, 5 adversarial, 2 status). Add BlockVolumeStatus struct and
Status() method. Includes QA test files for CP1-CP4a. 940 total unit tests.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Primary ships WAL entries to replica over TCP (data channel), confirms
durability via barrier RPC (control channel). SyncCache runs local fsync
and replica barrier in parallel via MakeDistributedSync. When replica is
unreachable, shipper enters permanent degraded mode and falls back to
local-only sync (Phase 3 behavior).
Key design: two separate TCP ports (data+control), contiguous LSN
enforcement, epoch equality check, WAL-full retry on replica,
cond.Wait-based barrier with configurable timeout, BarrierFsyncFailed
status code. Close lifecycle: shipper → receiver → drain → committer →
flusher → fd.
New files: repl_proto.go, wal_shipper.go, replica_apply.go,
replica_barrier.go, dist_group_commit.go
Modified: blockvol.go, blockvol_test.go
27 dev tests + 21 QA tests = 48 new tests; 889 total (609 engine + 280
iSCSI), all passing.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
